You'd have to check the accelerometer's position at every frame using a low pass filter and compare it to a reference vector. You then can check the direction and/or the angle from the device's orientation to the reference vector. You can use this information to move a character around, etc. For example, you can use the angle difference to determine the character's speed.

I use the accelerometer to move a character around in my current project. It's really easy once you understand how it works. Unfortunately, I only use Playmaker for AI in my game. All else uses custom scripts that are sometimes linked to Playmaker FSMs.